通過接口的兩個片段之間的通信失敗

Question

我有一個主要活動，有兩個選項卡，每個選項卡是一個片段（frag1和frag2）。 frag1的佈局有三個文本視圖和一個按鈕，frag1 實現SensorEventListener並在三個文本視圖中顯示加速度計值，該按鈕用於將z軸的加速度計值傳遞給frag2。 Frag2只有一個帶有textview的佈局來顯示來自frag1的傳遞值。

這兩個片段之間的通信是通過一個接口實現的，該接口由承載frag1和frag2的主要活動實現。在運行時 當我按下frag1中的按鈕將加速器值傳遞給frag2時，儘管創建了frag2並且其視圖已準備就緒，但我仍然收到getView = null。

下面我公佈的主要活動，frag1和frag2，請大家幫我看看爲什麼我每次按下按鈕時，通過從frag1到frag2東西的價值，顯示和 getView是空

主活動：

public class MainActivity extends AppCompatActivity implements IDataPasser{ 

private Toolbar mTB = null; 
private TabLayout mTL = null; 
private ViewPager mVP = null; 
private VPagerAdapter mVPAdapter = null; 

private Frag_2 mFrag2 = null; 
private Frag_1 mFrag1 = null; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    this.initViews(R.layout.activity_main); 
    this.initObjs(); 
} 

private void initViews(int rootView) { 
    setContentView(rootView); 

    this.mTB = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(this.mTB); 

    this.mTL = (TabLayout) findViewById(R.id.tab_layout); 
    this.mTL.addTab(this.mTL.newTab().setText("Tab 1")); 
    this.mTL.addTab(this.mTL.newTab().setText("Tab 2")); 
    this.mTL.setTabGravity(TabLayout.GRAVITY_FILL); 

    this.mVP = (ViewPager) findViewById(R.id.pager); 
    this.mVP.setOffscreenPageLimit(1); 
} 

private void initObjs() { 

    this.mFrag2 = new Frag_2(); 

    this.mVPAdapter = new VPagerAdapter(getSupportFragmentManager(), this.mTL.getTabCount()); 
    this.mVP.setAdapter(this.mVPAdapter); 

    this.mVP.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(this.mTL)); 
    this.mTL.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() { 
     @Override 
     public void onTabSelected(TabLayout.Tab tab) { 
      mVP.setCurrentItem(tab.getPosition()); 
     } 

     @Override 
     public void onTabUnselected(TabLayout.Tab tab) { 

     } 

     @Override 
     public void onTabReselected(TabLayout.Tab tab) { 

     } 
    }); 
} 

@Override 
public void onValChanged(float val) { 
    this.mFrag2.fromFrag1(val); 
} 
} 

frag1：

public class Frag_1 extends Fragment implements SensorEventListener{ 

private final String TAG = this.getClass().getSimpleName(); 

private IDataPasser mPasser; 

private View mRootView = null; 
private TextView mtvAccX = null; 
private TextView mtvAccY = null; 
private TextView mtvAccZ = null; 
private Button mbtnPass = null; 

private SensorManager sensorManager; 

float x; 
float y; 
float z; 

@Override 
public void onAttach(Context context) { 
    super.onAttach(context); 
    Log.w(TAG, "onAttach()"); 

    this.mPasser = (IDataPasser) context; 
    sensorManager = (SensorManager) getActivity().getSystemService(Context.SENSOR_SERVICE); 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    Log.w(TAG, "onCreate()"); 

} 

@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    Log.w(TAG, "onCreateView()"); 

    this.mRootView = inflater.inflate(R.layout.frag_1, container, false); 

    this.mtvAccX = (TextView) this.mRootView.findViewById(R.id.frag1_x); 
    this.mtvAccY = (TextView) this.mRootView.findViewById(R.id.frag1_y); 
    this.mtvAccZ = (TextView) this.mRootView.findViewById(R.id.frag1_z); 
    this.mbtnPass = (Button) this.mRootView.findViewById(R.id.frag1_btn_pass); 

    return this.mRootView; 
} 

@Override 
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 
    Log.w(TAG, "onViewCreated()"); 
} 

@Override 
public void onActivityCreated(@Nullable Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 
    Log.w(TAG, "onActivityCreated()"); 

    Sensor accSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
    sensorManager.registerListener(this, accSensor, sensorManager.SENSOR_DELAY_FASTEST); 

    this.mbtnPass.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      mPasser.onValChanged(z); 
     } 
    }); 
} 

@Override 
public void onStart() { 
    super.onStart(); 
    Log.w(TAG, "onStart()"); 
} 

@Override 
public void onResume() { 
    super.onResume(); 
    Log.w(TAG, "onResume()"); 
} 

@Override 
public void onPause() { 
    super.onPause(); 
    Log.w(TAG, "onPause()"); 
} 

@Override 
public void onStop() { 
    super.onStop(); 
    Log.w(TAG, "onStop()"); 
} 

@Override 
public void onDestroy() { 
    super.onDestroy(); 
    Log.w(TAG, "onDestroy()"); 
} 

@Override 
public void onSensorChanged(SensorEvent event) { 

    switch (event.sensor.getType()) { 
     case Sensor.TYPE_ACCELEROMETER: 
      float[] values = event.values; 

      x = values[0]; 
      y = values[1]; 
      z = values[2]; 

      this.mtvAccX.setText(String.valueOf(x)); 
      this.mtvAccY.setText(String.valueOf(y)); 
      this.mtvAccZ.setText(String.valueOf(z)); 
      break; 

     default: 
      break; 
    } 
} 

@Override 
public void onAccuracyChanged(Sensor sensor, int accuracy) { 

} 
} 

frag2：

public class Frag_2 extends Fragment { 

private final String TAG = this.getClass().getSimpleName(); 

private View mRootView = null; 
private TextView mtvText = null; 

@Override 
public void onAttach(Context context) { 
    super.onAttach(context); 
    Log.w(TAG, "onAttach()"); 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    Log.w(TAG, "onCreate()"); 
} 

@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    Log.w(TAG, "onCreateView()"); 

    this.mRootView = inflater.inflate(R.layout.frag_2, container, false); 
    this.mtvText = (TextView) this.mRootView.findViewById(R.id.frag2_tv_z); 

    Log.v(TAG, "getView(): " + getView()); 
    return mRootView; 
} 

@Override 
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 
    Log.w(TAG, "onViewCreated()"); 

    Log.v(TAG, "getView(): " + getView()); 
} 

@Override 
public void onActivityCreated(@Nullable Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 
    Log.w(TAG, "onActivityCreated()"); 
} 

@Override 
public void onStart() { 
    super.onStart(); 
    Log.w(TAG, "onStart()"); 
} 

@Override 
public void onResume() { 
    super.onResume(); 
    Log.w(TAG, "onResume()"); 
} 

@Override 
public void onPause() { 
    super.onPause(); 
    Log.w(TAG, "onPause()"); 
} 

@Override 
public void onStop() { 
    super.onStop(); 
    Log.w(TAG, "onStop()"); 
} 

@Override 
public void onDestroy() { 
    super.onDestroy(); 
    Log.w(TAG, "onDestroy()"); 
} 

public void fromFrag1(float val) { 
    if (getView() != null) { 
     this.mtvText.setText(""+val); 
    } else { 
     Log.e(TAG, "getView = null"); 
    } 
} 
} 

Answer 1

相反getView的（），您可以使用mRootView值來檢查它是否爲空或不是。

檢查此答案https://stackoverflow.com/a/9505298/1320616